Speed Calculator

[BrianG]

lol, the calc is pretty accurate for the most part. The user on the other hand...

Also, was working on figuring the ratios for the new emaxx (3905) tranny. It seems that the two-speed setup is a little more involved than the original; first gear has two actual ratios, while second only has one ratio. The Savage tranny kinda works the same way (somewhat), so I'm gonna do some code changes to allow multiple ratios in the tranny drop-down for these types of vehicles. Until the code is updated, here is a quick-n-dirty diagram showing the placement of the gears and the ratios:



Single speed (stock) and Two-speed second gear ratio = 1.83:1
Two-speed close-ratio first gear ratio = 2.96:1
Two-speed wide-ratio first gear ratio = 5.08:1

[BrianG]

Update to the calc:

- Added transmission ratios for the new Emax (3905)

- Changed the code for transmission ratios to show and calculate multiple ratios. Before, any additional transmission ratios had to be entered somewhere else.

- Updated Neu motor data for 1527, 1521, 1515, 1512, and 1509 series. Also added any newly listed motors in these series.

- Added Neu 1506 series motor data.

- Fixed bug with the picture viewer where parts of the image would not display.

[lutach]

Originally Posted by BrianG

Update to the calc:

- Added transmission ratios for the new Emax (3905)

- Changed the code for transmission ratios to show and calculate multiple ratios. Before, any additional transmission ratios had to be entered somewhere else.

- Updated Neu motor data for 1527, 1521, 1515, 1512, and 1509 series. Also added any newly listed motors in these series.

- Added Neu 1506 series motor data.

- Fixed bug with the picture viewer where parts of the image would not display.

You should add the Mega motors as well. I know they can go up to 74000rpms, but I haven't heard of anyone going that high yet.

[BrianG]

Added a power calculator to determine power drawn from the batteries based on pack voltage, pack capacity, and runtime. Yeah, I was bored...

Brian,

Could you please add the Muggy diff ratios in the speed calq?

[BrianG]

What are the ring/pinion gear tooth counts?

I'll add that as well as the Mega motors tomorrow...

[macr0w]

When entering voltage and battery cell size into the speed calculator do you guys put 4 cells at 3.7 volts per cell or what?

Because as we all know that's only 14.8 volts. My Polyquest 5000 mah 4s charges up to 16.8 volts fully charged.

That is a significant difference in voltage and there for RPM right?

[BrianG]

Ture, lipos peak at 4.2v/cell, but the voltage does not stay there very long at all when running - just take a look at any discharge graph. People generally use 3.7v/cell because that is the voltage the cell is at for the majority of the time. As a matter of fact, depending on setup, the voltage may actually fall to 3.5v/cell or lower during higher current bursts.

Also, it depends somewhat on the user.

- If you are looking for max torque specs, use a lower voltage/cell rating. High torque is generated by high current. High current causes the cell voltage to drop.

- If you are looking for max speed spec, there will be less current draw when the motor is spun out, but the cell still won't be at 4.2v because the current drawn will still pull the voltage down.

It depends on gearing and weight too. If you are geared high and/or have a heavy vehicle, expect more v drop on take-off acceleration due to the current needed. If geared low and/or have a lighter vehicle, v drop will be less.

It also depends on the battery quality and capacity/C rating. A higher quality/capacity/C rating battery will maintain a more constant voltage under load.

[brushlessboy16]

Brian could you add some specs for Outrunners?

[BrianG]

I generally limit the motor choices to what Mike carries. As you can see, the motor list is getting quite long already. As a mattery of fact, I'm thinking of removing the LMT motors altogether...

[lutach]

Originally Posted by BrianG

I generally limit the motor choices to what Mike carries. As you can see, the motor list is getting quite long already. As a mattery of fact, I'm thinking of removing the LMT motors altogether...

Please add the Megas Acn22 series.

[BrianG]

I will. I was waiting for the Muggy diff ratio from BlackedOutRevo...

[macr0w]

Originally Posted by BrianG

Ture, lipos peak at 4.2v/cell, but the voltage does not stay there very long at all when running - just take a look at any discharge graph. People generally use 3.7v/cell because that is the voltage the cell is at for the majority of the time. As a matter of fact, depending on setup, the voltage may actually fall to 3.5v/cell or lower during higher current bursts.

Also, it depends somewhat on the user.

- If you are looking for max torque specs, use a lower voltage/cell rating. High torque is generated by high current. High current causes the cell voltage to drop.

- If you are looking for max speed spec, there will be less current draw when the motor is spun out, but the cell still won't be at 4.2v because the current drawn will still pull the voltage down.

It depends on gearing and weight too. If you are geared high and/or have a heavy vehicle, expect more v drop on take-off acceleration due to the current needed. If geared low and/or have a lighter vehicle, v drop will be less.

It also depends on the battery quality and capacity/C rating. A higher quality/capacity/C rating battery will maintain a more constant voltage under load.

I did some speed runs back and forth in front of my house on and off for 30 minutes or so and still had 15.4 volts on my battery this afternoon.

It was SCREEEEAAAMING!!!! The speed and acceleration is mind blowing! I now know what "Stupid Fast" really means.

[Patrick]

Originally Posted by macr0w

I did some speed runs back and forth in front of my house on and off for 30 minutes or so and still had 15.4 volts on my battery this afternoon.

That would be unloaded voltage though. Voltage under load is what's most important, and is one of the main differences between a good battery and a not so good battery. 15.4v does mean that the pack probably had about half is capacity left though.

[macr0w]

Yeah, it's a 25c 5000 mah 4s Polyquest/Enerland pack.

So far I'm really happy with it.